1. Technical Field
The present invention relates to a cross-linked polymer and a process for producing the same, an absorptive structure and an absorptive article. More particularly, the present invention relates to a cross-linked polymer having the extremely excellent water-retaining capacity and absorbing capacity under load and a process for producing the same, an absorptive structure and an absorptive article.
2. Background Techniques
Previously, it has been demanded that cross-linked polymers used in absorbing articles such as a paper diaper have the large water retaining amount and the large absorbing amount under load, and many improvements have been tried by a number of methods. As a method for enhancing the water retaining amount, there have been proposed a method of using a chain transfer agent such as a thiol compound (JP-A 3-179008) and the like in addition to the method of optimization by varying an amount of an polymerization initiator, a polymerization temperature, a polymerization concentration and the like. On the other hand, as a method for enhancing the absorbing capacity under load, there has been proposed a number of methods of treating a part near the surface of a polymerized particle (JP no. 267529, EPA618005 etc.)
However, according to these methods, the properties are necessarily biased, a cross-linked polymer does not satisfy both the water retaining capacity and absorbing capacity under load at the same time and, for this reason, when used in absorbing article, the absorbing capacity is not sufficient and, thus, further improvement is desired. The present inventors studied intensively in order to obtain a cross-linked polymer exhibiting the excellent absorbing capacity when used in absorbing article, which resulted in completion of the present invention:
An object of the present invention is to provide a cross-linked polymer satisfying both water retaining capacity and absorbing capacity under load at the same time and a process for producing the same. Another object of the present invention is to provide an absorptive structure and absorptive article exhibiting the excellent absorbing capacity when the present cross-linked polymer is applied to hygiene articles such as physiological napkins.